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What are the three things that define short term memory?
- 1. last seconds to minutes
- 2. very limited
- 3. dependent on persistent activity in the prefrontal and parietal cortices
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What are the three thins that define long term memory?
- 1. lasts days to years
- 2. nearly unlimited
- 3. depend on gain and loss of synapses and structural changes in the neurons
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Working memory is persisent on
C) higher order brain regions
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long term memory can be defined by ___
new spine and dendrite growth
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What are the four type of tools to study neural basis of memory?
- 1. patients with brain lesions
- 2. brain imaging (fMRI, PET)
- 3. Electrophysiology
- 4. surgical manipulations in primates
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What is thought to mediate working memory?
stimulus specific persistent activity in the PFC
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How is working memory tested on animal models?
electro-recording of PFC neurons persistently firing despite the stimulus is removed during the delay period.
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What are the two hypothesis of neural mechanisms for short term memory?
- A. persistent intrinsic firing
- B. persistent reverberatory network activity
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What is the persistent intrinsic firing hypothesis for short term memory?
neurons in the PFC can act like a switch when driven hard enough by the stimulus, it will maintain firing properties
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What is the persistent reverberatory network activity hypothesis for short term memory?
- there is highly connected neural circuits that synapse on to each other in the cortical area.
- These excitatory connections when driven, generate a synaptic activity to maintain the system in an active state, even in the absence of an input
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What brain region does long term memory activate?
temporal lobe (hippocampus is critical)
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What cortex regions are needed for long term memory within the temporal lobe?
- a. perirhinal cortex
- b. entorhinal cortex
- c. parahippocampal cortex
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What's the deal with H.M. ?
- had epilepsy, and had much of temporal lobe, hippocampus, entorhinal cortex, and amygdala bilaterally removed to control for seizures.
- but suffered from anterograde amnesia and could not remember new info, however his old long term memory and motor skill learning still intact
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What did it tell us about memory formation from patient H.M.?
The temporal lobe is critical for making new memories, but not necessary for all types of memories, such as motor skill learning.
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How does lesion in primary sensory cortices affect priming memory?
It abolishes priming memory
eventhough memories can be 'primed' in amnesic patients
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What are the two types of long term memory?
- implict (nondeclarative)
- explict (declarative)
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Explicit memory depends on
B) hippocampus
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Implicit memory depends on
basal ganglia and cerebellum
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Implicit(non-conscious) memory involves
- priming
- skills and habits
- classical and operant conditioning
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Explicit (conscious) memory involves
- facts (semantic)
- events (epidodic)
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How is explicit memories recalled?
prefrontal to temporal lobe connections are critical for recall???
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What is the basis of classical (Pavlovian) conditioning?
US + CS -> CR
- unconditioned stimulus: food
- conditioned stimulus: tone
- unconditioned response: drool to food
- conditioned response: drool to tone
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Fear conditioning is dependent on
B) temporal correlation
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What was the experiment done to test fear conditioning?
CS and US have to be paired simuntaneously to strenghten condition to max
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Where do the neural circuits of (US//tone) audition and (CS//shock) somatosensory converge for fear conditioning?
Converging in the amygdala, pairing strengthens the CS input to drive the fear response
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What is the underlying cause of fear conditoning with LTP?
Hebbian long term chagnes in synaptic strength in the amygdala
LTP driven by fear conditoning-- associative plasticity
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